Vortices and Large-Scale Structures in a Rough Open-Channel Flow Subjected to Bed Suction and Injection

Abstract

The effect of seepage (injection and suction) on the dynamics of vortices and large-scale structures in a rough open channel flow was examined experimentally. The velocity measurements in the open channel flow were carried out using particle image velocimetry. A swirling strength-based vortex identification algorithm was used to extract the location, size, and strength of vortices in the flow. Proper orthogonal decomposition (POD) was used to analyze the dynamics of large-scale structures in the flow. The results indicate that suction induces a greater change compared with an equivalent amount of injection on the open channel flow. Suction dampens the size and strength of the vortices compared to the no-seepage case. POD analysis indicates that seepage tends to introduce more small-scale structures in the flow and destroys the large-scale organized motion present otherwise in the flow.